1. Field of the Invention
The present invention relates to an engine mount structure and more particularly to an engine mounting device suitable for the safety designing of a vehicle.
2. Prior Art
A wide variety of engine mounting devices have been proposed to elastically support a power plant such as an engine. For example, Japanese Patent Application Laid-open No. Toku-Kai-Hei 3-168425 discloses a mounting device in which an elastic member is interposed between an inner cylinder and an outer cylinder and a stopper integrally formed with these cylinder members is disposed such that its contact surface is in parallel with the axis of the mounting device in order to restrict an excessive displacement in the orthogonal direction of the axis.
Further, as a second example, there is amounting device in which an inner cylinder is press-fitted to a rubber bushing vulcanized to an outer cylinder and a bracket of the mounting device is formed by synthetic resin.
Further, citing a third example, as shown in FIG. 5, there is a mounting device comprising an engine mount 21A made of metal and a body mount 21B incorporating a cushion rubber. The engine mount 21A is connected to an engine through bolt holes 28A, 28B. Further, bolts 31A, 31B of the body mount 21B are inserted in bolt holes 30A, 30B and are fastened by a nut 32, thus the engine mount 21A being connected with the body mount 21B. A stopper 25 is provided on an extended part of an under plate of the body mount 21B and is enclosed by a stopper holder 26 so as to be allowed to move within a specified range of the stopper holder 26. Further, a heat shield plate 33 is provided to protect. the cushion rubber of the body mount 21B from heat radiation of an exhaust system.
Generally, a stopper of a mounting device provided between an engine and a body acts as restricting a displacement of the engine when such a light impact as not deploying an air bag is applied to the engine. Accordingly, on a light impact, the engine restores an original position without breaking the stopper and the mounting device. When a large impact is applied to the engine in such a manner as deploying an air bag, the engine is largely displaced to break the stopper. As a result, the mounting device is broken and the engine is disconnected from the body to fall down.
According to the first example of the prior art, its object is to restrict an excessive displacement of the stopper and no consideration is paid to the disconnection of the engine.
Further, in the second example of the prior art, the bracket is fabricated of synthetic resin only for the purpose of weight reduction and the disconnection of the engine is not disclosed.
Further, according to the third example, the disconnection of the engine is taken into consideration, however it is difficult to estimate a correct break point of the stopper because all component parts are made of metal and further those are connected by welding. Therefore, this prior art has a difficulty in tuning the countermeasure for impact.